1. Field of the Invention
This invention relates to the control of heating and air conditioning systems and particularly to the control of such systems which incorporate the "heat zone" or the "heat balance" concept.
2. Description of the Prior Art
Systems for the maintenance of proper environment temperature control within buildings have long been known with the earliest of such environmental control heating systems being open flame fires. Heating systems for buildings have gradually evolved utilizing a variety of fuel means and utilizing a wide variety of techniques for the transfer of heat from the heat source to the occupied areas of the building. These techniques include forced draft systems, hot air systems, hot water systems, steam systems in enclosed pipes and similar systems. Similarly, air cooling systems for buildings slowly evolved with a number of different systems being well known in the art. These include conventional chilled water systems as well as various types of pressurized systems utilizing different freon refrigerants.
As designs for environmental control systems for buildings have become increasingly more sophisticated, designers have recognized that numerous sources of heat are typically available inside buildings and that these sources of heat can be used to supplement the normal building heating system, thus minimizing the amount of applied fuel required to heat the building. Such additional sources of heat include the sensible heat given off by the people within the building due to their respiration and due to heat transfer between the building internal atmosphere and the individual's human skin, heat emanating from light fixtures, heat produced by various kinds of machinery, and various other heat sources. Designers have found it desirable for efficient heating of a building to utilize all of these sources of heat to the maximum extent possible, so that the designers can minimize the amount of applied fuel required to heat the building. Typical of the devices which have been utilized to take advantage of this general concept are the devices described in the U.S. Pat. No. 3,699,184, issued to Franzreb, and the U.S. Pat. Nos. 3,193,001, 3,420,439 and 3,424,233 issued to Meckler.
As designs progressed, designers found that no heat was required for certain interior portions of some buildings due to the high rate of internal heat generation caused by a high desity of people, by lighting fixtures, or by other factors. In fact, designers found that in many buildings and especially in large office buildings that it was required to affirmatively remove heat from the more interior sections of the building via air conditioning, even during the winter, in order to maintain those interior portions of the building at a comfortable temperature. At the same time it was found that more exterior portions of these buildings generally required heat to be introduced to those sections during the winter months. This is because the building loses heat through its exterior walls and windows to the outside atmosphere.
With these factors in mind, the heat zone or heat balance principle came to be utilized whereby portions of a building which had differing heat requirements during the winter season were categorized as zones and systems were developed to transfer heat from one zone to another. In such systems, the totality of zones in combination with the heating and air conditioning apparatus is referred to as "the system" and heat is discarded from the system only when there is an overall excess of heat in the entire system. In the heat zone concept, if one zone has an excess of heat while another zone has a heat deficit, heat is transferred from the zone with the excess to the zone in which the deficit exits. Generally, only when there is a heat deficit in the system as a whole is an external heat generation source called on to supply heat for those zones of the system which require it.
All buildings are subject to a gain in the amount of heat inside the building due to light, people and equipment inside the building and due to solar energy which is incident on the building. Heat gained through these sources is usually of a sufficient quantity to completely satisfy the heating requirement for the building through a large part of the normal winter heating season, if the building is located somewhere in the earth's temperature zone. Unfortunately, most of the heat which is generated inside the building is generated in areas of the building that have little or no heat transmission loss to the outside or to the other parts of the building which require heat during the winter. Accordingly, most of the heat becomes waste heat energy which is not useable and which must be removed from the interior area of the building in order to maintain the interior of the building at a comfortable temperature. Thus, this heat energy is lost if it is exhausted to the atmosphere. It is apparent that heat recovery is desirable to transfer such potentially wasted heat energy to those areas of a building which require net heat input, due to heat transmission loss through the building walls and due to heat loss due to the ventilation system during the winter season. Additionally, such potentially wasted heat could be used for a plurality of other energy requirements.
Such excess heat energy is conventionally difficult to obtain in a useable form because it exists at a temperature level which is too low for the efficient, direct transfer of heat to areas having a need for net heat input. To render the excess heat energy useful, the temperature of the medium in which this heat energy exists must be raised. This is accomplished in the present invention by application of a standard refrigeration cycle, which requires a small energy input and which provides a portion of the excess heat energy as available heat energy output. Using this approach, the ratio of output heat to input heat can be on the order to 5:1; this is greatly in excess of the best obtainable ratio of 1:1 when heat energy, input to areas having need for net heat input, is directly applied from an external source such as a boiler or other fueled means.
Internal heat is generated at a fairly constant rate in most buildings. Many modern buildings are equipped with a year-round environmental control system which may comprise a conventional heating system and a convention cooling system where these two systems together are operated as needed to maintain the building at a comfortable temperature level. During the summer season, substantially the entire heat load must be removed from the building and rejected to the atmosphere by application of a conventional refrigeration cycle. During the winter season it is customary to use the cooling capacity of cool outdoor air to remove excess heat which is generated in areas of the building having little or no inherent heat loss, such as the more interior areas of the building which do not border on outside walls, and to add heat from some external source to those areas having a net heat loss. Typically those are areas located along the outside walls of the building.
Heat recovery systems designed to capture and transfer excess heat from areas which require heat to be removed and designed to reject heat in areas requiring a net heat input have been known and are old in the art. However, the heat recovery systems which have been known heretofore have not used a balanced system approach where the basic system design goal is predictated on expending the minimum possible amount of energy required to perform the necessary heating function for areas requiring a net heat input, while the total system is simultaneously performing a net cooling function. In a building, so long as the internally generated waste heat equals or exceeds the total building heat loss, a net cooling load exists. This means that the building must be cooled to remove the internally generated waste heat in order to maintain the building at a comfortable temperature. In very cold weather, when building heat losses exceed the internally generated waste heat, heat must be added from an external source in order to prevent the building's internal temperature from dropping below a confortable level. When the building heat loss greatly exceeds the rate of internal heat generation, the excess heat in interior aras of the building can be easily transferred to the more exterior areas of the building. The more difficult problem arises when, during the winter heating, the total building net load is a cooling load. In this situation, the internally generated waste heat within the building exceeds the total building heat loss. Consequently, certain sections of the building must be cooled, due to high rates of internal heat generation, while other sections to the building must be heated, due to low rates of internal heat generation and high losses of heat to the outdoors. This situation is the situation which exists over the greater portion of the normal winter heating season. The balanced system of the present invention is designed to optimize the heating of the building on the basis of minimizing the energy input required to heat the building under these winter conditions.
In accordance with the foregoing, the present invention overcomes the disadvantages inherent in the prior art by providing a balanced system for operation of a standard refrigeration and air conditioning system and associated equipment, to accomplish both summer cooling and winter heating of a building. The present invention is applicable to most standard systems and to most equipment already used in the design of all-year environmental control systems for buildings. The present invention applies standard automatic temperature control components to operate the air conditioning system with a minimum of external heat required for input to the building system. The present invention also utilizes an air conditioning system comprised of standard water chilling equipment and forced air circulating equipment. During winter operation of the present invention, the refrigeration cycle is utilized only as required for heating purposes, for areas of the building which require a net heat input, while outdoor air is used as required to satisfy any net remaining cooling load. The present invention provides a system which will automatically control the operation of the water chiller of the refrigeration system, during winter cycle operation, for the recovery and transfer of waste heat from areas of a building having excess heat due to a high rate of internal heat generation. The present invention further provides a system for automatic control of the air handling apparatus in any zone which acts to provide for the absorption of waste heat and to provide for the transfer of such waste heat to a chilled water cooling circuit, in the proper amount, to satisfy various heating requirements. This control is affected while the net cooling load for the building is simultaneously being satisfied by the introduction of cool outside air.